1. Field of the Invention
The present invention relates to a line-inserting method, a line for inserting and an optical transmission line for inserting.
2. Description of the Related Art
U.S. Pat. No. 4,498,659, as a first prior art of the present invention, discloses the technique of connecting a flexible plastic cone member having an external diameter approximately equal to the internal diameter of the conduit to an end of a line for inserting a cable, pushing the flexible plastic cone member into the conduit from one end thereof, and blowing air into the conduit or sucking air therefrom, whereby the flexible plastic cone member is moved to the opposite end of the conduit.
U.S. Pat. No. 3,119,600, as a second prior art of the present invention, discloses the technique of pushing a soft ring member provided around a hose of a vacuum suction device into one end of the conduit.
U.S. Pat. No. 3,301,531, as a third prior art of the present invention, discloses the technique of pushing a soft ring member provided around a hose of a blower device into one end of the conduit.
In the second and third prior arts, a spherical member having an external diameter approximately equal to the internal diameter of the conduit is connected to an end of a line to be used for inserting a cable to give a thrust to the line.
These prior arts, however, intend to generate a thrust for inserting the line into the conduit, using the difference in pressure on both sides of the cone member or spherical member, each having an external diameter approximately equal to the internal diameter of the conduit, and consequently has the following problems.
In the case rust and foreign substances are attached to the inner surface of the conduit, or in the case another cable has been already inserted in the conduit, the cone member or spherical member excessively increases the friction resistance against the inner surface of the conduit or already inserted cable so that the line has not been readily inserted. In the case the conduit has right-angled corners or greatly curved portions, the line is pressed against inner surfaces of the right-angled corners or greatly curved portions to generate a great friction resistance although the line is pulled by the cone member and spherical member so that the line has not been readily inserted. For these reasons, the conventional pneumatic line-insertion system has not been widely put into practical application.
The second prior art which discloses the technique of pushing one part of the soft ring member of the hose into one end of the conduit, and sucking air from the conduit via the hose has the following problems.
First, since the soft ring member is pushed into one end of the conduit in the ring-like configuration, the cone member or spherical member which has moved within the conduit are obstructed by this soft ring member so as not to be drawn from the end of the conduit.
Next, the conduit has a specific one or small number of fixed internal diameters. So, a specific part of the conical outer surface of the soft ring member is continuously pressed on one end of the conduit, and consequently, the life of the soft ring member has become short. In the case the conduit which has been embedded in the wall is connected to a joint box, for example, the soft ring member has not been readily inserted into the joint box.
In the case another cable has been already inserted in the conduit, the end of the conduit is narrowed with both the cable and soft ring member, and cannot be sealed sufficiently. This results in the air flow in the conduit becoming worse to decrease the thrust to be applied to the line for inserting the cable into the conduit.
It is an object of the present invention to provide a new line-inserting method, a new line for inserting and a new optical transmission line for inserting, which can help line-inserting into a conduit.
The line-inserting method of the present invention makes air stream into a tubular conduit(pipe for accommodating a electric cable or a communication line) and carries the line member having a tape of which a main surface is given fluid mechanical thrust by the air stream flowing along the main surface of the tape.
Almost pulling force given to the tape in the air stream is generated by the fluid mechanical thrust and little pulling force given to tape in the air stream is generated by the friction between the main surfaces of the tape and the air stream. The fluid mechanical thrust generated on the main surfaces of the tape by the air stream is typically known as a wing theory in fluid mechanics. The tape performs like a wing of the aircraft in the air stream nevertheless the tape is very thin and very soft when it is compared to the wing. Nevertheless, the thin and soft plastic tape generates a large thrust in the air stream. For the inventor, it was the large mystery. Now, the inventor may understand the true reason about easy flight of the thin and soft plastic tape in the pipe.
The thin, soft and light plastic tape is bended easily in the air stream like wave-shape and flutters. The surface shape of the bending portions of the tape is almost same as the surface shape of the wing and bends the air stream like the wing. The wing generates the large floating force and resistive force when it is compared to a plane disposed in parallel to the air stream. The resistive force generated on the bending surface of the tape becomes the fluid mechanical thrust pulling the tape into the pipe.
The second advantage of use of the fluid mechanical interference between the main surfaces of the tape and the air stream is that the contact between the inner surface of the pipe(tubular conduit) and the tape at the sharp corner of the pipe. Its reason is that the tape is bended strongly and the large resistive force generates on the tape near the corner. Further, the air stream pushes the tape to the direction to leave from the corner. Consequently, the friction between the tape and the corner does not occur. It means the tape can fly in the pipe easily over the corner of the pipe.
The third advantage of use of the fluid mechanical interference between the main surfaces of the tape and the air stream is that the tape can fly easily into the pipe if the barrier like the cable is installed in the pipe because the thin and soft tape can easily bend along the bending air stream for avoiding the barrier. As the results, the tape can fly into the pipe having the barrier without damage when it is compared to the present stainless line for inserting cable.
The fourth advantage of use of the fluid mechanical interference between the main surfaces of the tape and the air stream is that the top portion made of the tape does not generate the large friction when it is compared to the top portion of the line with a half ball-shape disclosed by the prior patents. Such as top portion with the half ball-shape moves by the difference of the pressures. This top portion with the half ball-shape requires to decrease the air leakage into the gap between the top portion and the inner surface of the pipe. As the results, the hard top portion with the half ball-shape attaches to the inner surface of the pipe and the large friction generates. The tape-shape top portion of the present invention does not have such problem and can fly easily.
The fifth advantage of use of the fluid mechanical interference between the main surfaces of the tape and the air stream is that this fluid mechanical thrust is generated every portion of the tape. As the results, the tape does not need to have the strong anti-tension force and can have a thin thickness when it is compared the line pulled by the top portion with the half ball-shape or the cone-shape. Such line pulled the only top portion has a strong anti-tension force and become heavy and hard to move. The tape-shape top portion of the present invention does not have such problem and can fly easily.
The sixth advantage of use of the fluid mechanical interference between the main surfaces of the tape and the air stream is prefer to insert the line between two selected ports in ports of the pipe network. If the other ports are covered by the cover plates, the air stream is occurred from one port (the inlet port) to the another port (the outlet port) easily and the tape fly from the inlet port to outlet port by the air stream. Contrary to this, the flying line by the difference of the pressures which is made at the top portion of the line, is easily stuck at the point of the covered port because the large top portion of the line may changes its own proceeding direction at that point and the one part of the top portion and collides to the corner of said covered port.
The seventh advantage of use of the fluid mechanical interference between the main surfaces of the tape and the air stream is to use the ordinary and cheap material.
Further, the present invention is explained as follows. The conventional cone-like head or spherical head has an external diameter approximately equal to the internal diameter of the conduit so that when rust and foreign substances exist on the inner surface of the conduit, a great friction resistance is generated between the cone-like or spherical head and the inner surface of the conduit. This results in the insertion of the line being blocked, and, in some cases, the cone-like or spherical head being obstructed by these obstructions to stop in the tubular conduit. This problem is especially remarkable when another cable has been already inserted in the conduit.
In contrast, the head of the present invention, which has the tape, or tapes, scarcely causes any problem even when rust and foreign substances exist on the inner surface of the conduit, or cables are already placed within the tubular conduit. Consequently, the head (top portion) with tape-shape of the present invention can move in the conduit while pulling the line.
With the conventional technique, the line is pulled by the force generated due to the difference of static pressure which is applied to the cone-like head or spherical head. In contrast, with the technique of the present invention, the line is pulled by a fluid mechanical resistance force which is applied to the surface of the tape from a high speed fluid flow. In accordance with the present invention, the end of the line need not be held in nearly contact with the inner surface of the conduit to ensure such a difference of static pressure, and consequently, the head of the line is hardly caught by the already inserted cable and foreign substances existing on the inner surface of the conduit so that the movement of the head of the line is hardly obstructed thereby. In accordance with the present invention, if such foreign substances exist within the conduit, fluid flows at a high speed around them so that tape-shape head of the line also moves within the conduit automatically around these foreign substances.
If the conduit curves at approximately a right angle, the tape in accordance with the present invention preferably generates a thrust. This is caused by the fluid mechanical resistance force being applied to every portion of the tape while it flows along the right-angled part of the conduit, to force the tape therealong. In contrast, the conventional cone-like and spherical heads are difficult to move smoothly along the right-angled part of the conduit due to the configuration thereof, whereby a desirable thrust cannot be readily obtained. In accordance with the present invention, as the conduit curves greatly, the tape generates a greater fluid mechanical resistance force against the high speed fluid flow.
Furthermore, the present invention also has the operational advantage that, if one part of the tape is caught by any obstruction existing on the inner surface of the conduit, the tape separates from the obstruction immediately so that the tape is not caught by the obstruction permanently.
Said advantage will be explained with reference to FIG. 19. Reference numeral 1000 designates the tape which is blown and forced in a conduit 2000 with a high speed air flow 3000. When the tape 1000 flies in a right-angled portion 2001 of the conduit 2000, it curves, as shown in FIG. 19, and the high speed flow 3000 collides against a most curving part 1001 of the tape 1000, and a hydrodynamics buoyancy Ff and a drag (thrust) Fr are generated. Symbol x indicates the longitudinal direction of the tape at the most curving part 1001. As is known form FIG. 19, a force F is applied to the most curving part 1001 in such a direction as to separate it from a corner 2002 of the right-angled portion 2001. This results in that, if the most curving part 1001 receives a thrust Fh from the head (not shown), it is not strongly pressed against the corner 2002. Consequently, the tape 1000 smoothly flies by the thrust Fr and never contact to the corner 2002 by the force Ff generated by the high speed flow of the air stream 3000 if the conduit has plural corners. In FIG. 19, the side surface (thickness direction) of the tape 1000 is illustrated.
FIG. 20 illustrates the case a line 1010 is made of the thread pulled by the large head (not shown) generated the difference of pressure. Since fluid power is scarcely applied to the fine thread 1010, the most curving part 1011 thereof is strongly pressed against the corner 2002 of the right-angled conduit 2001 to generate a great friction resistance, and consequently, to block the insertion of the thread 1010, in some cases, cut the thread 1010.
In accordance with the present invention, the line member may have both of the thread and the tape. It is preferable to compose the threads of carbon fibers and polyamide fibers, each exhibiting an excellent tension resistance, and to compose the tape of a plastic resin which is obtained at low cost. With this arrangement, the line member which has a required tensile strength and deforms readily to exhibit hydrodynamic performance can be effected at low cost. Of course, this arrangement may be adopted as that of the head. The line member having a tape can be wound on a reel member like a reel attached to a fishing rod, thus enabling the line member to be readily retracted or drawn out for use.
The technical reason of the great thrust of the tape in the air stream is explained as bellows. If the main surface of the tape is flat, the thrust of the tape is made by the only friction and it is very small. However, the air stream is not constant and has many small whirlpools and many small disorders. By these confusion or un-uniformity, the tape has many small bending portions. If small bending portions are made, the fluid mechanical forces Ff and Fr (shown in FIG. 19) are generates by the air stream. the bending portions are still small and the fluid mechanical forces Ff and Fr (shown in FIG. 19) are small. However, the bending portions naturally develops by the fluid mechanical forces F and the force F become large by the large bending portions. After the large bending portions extremely becomes large, the shape of the large bending portions become the barrier against the air stream and the air stream changes the direction of the force F. As the results, the force F makes the bending portions small.
This change of the shape of the bending portions can not stop at the instant that the surface of the tape become flat by the inertia of the tape. Then the bending portions start to bend in the opposite direction. Consequently, the bending portions alternatively occurs in the both direction of the thickness of the tape and the fluid mechanical force F is continuously generated. Further, the whirlpools of the air stream flows toward the downstream and gives the bending force to the downstream portion of the tape by the pressure difference between the both of the main surfaces of the tape because the pressure of the air stream changes by arrival of the whirlpool. This may be the reason of the fluttering of the flag in the strong wind.
In one preferred embodiment, the tape is longer than the tubular conduit. As the results, every portion of the tape in the pipe can generate the thrust until the top portion of the tape reaches to the outlet port of the pipe.
In another preferred embodiment, the line member pulls the larger line means like an electric cable or an communication cable. The cable includes a metal cable and an optical fiber cable. Such as line member can be used instead of the present preliminary line for inserting cables.
In another preferred embodiment, the line member has a thread for reinforcing the tape. As the results, the tape become more strong and can pull a heavy large line means.
In the other preferred embodiment, the line member has a thread portion without the tape. The thread for fishing is desirable as the thread portion. Because the thread portion has a small friction and resistivity to the air stream, the tape portion of the line member can fly into the long pipe and pull the thread portion easily. In the other preferred embodiment, the top portion of the line member is consisted of plural tapes. As the results, this top portion can generate a strong pulling thrust. In the preferred embodiment, the tape can have the thickness of 0.005-0.1 mm, the width of 5-100 mm and the length of 5-500 m. The use of suction pipe is preferable to keep the cover plate keeping to cover the other ports of the tubular conduit.
In the preferred embodiment, a connecting hose connecting a suction as the air pump and the outlet port of the conduit is employed. The connecting hose has a elastic ring plate contacted to a surface of a wall around the outlet port. The negative pressure in the elastic ring presses the elastic ring to the surface of a wall around the outlet port of the conduit and decrease the air leakage into a gap between them.
In the preferred embodiment, a connecting hose connecting a suction as the air pump and the outlet port of the conduit is employed. The connecting hose has a visible window. As the results, The operator can find the arrival of the top portion of the tape easily.
The line for being inserted into a tubular conduit by air stream of the present invention has plural plastic resin tapes of which central portions in a width direction of the tapes is fixed each other (FIG. 4 or FIG. 13). This structure of the flying line in the conduit can generate a strong thrust and a small width compared with one tape type-line.
The optical transmission line of the present invention has an optical fiber and a thin plastic resin tape fixed to the optical fiber in the longitudinal direction of the optical fiber (FIG. 13). The tape for generating the fluid mechanical thrust in the air stream occurred in the tubular conduit and giving the thrust to the optical tape. It is well known that the optical fiber has very small diameter and is easy to be cut by small tension force at any portion of the optical fiber. So, the every optical fiber in prior arts has a cover tube and a wire to receive the pulling stress occurred at the pulling time. By employing the line-inserting method of the present invention, the stress of the optical fiber becomes very small because each portion of the optical fiber is given the thrust from the each portion of the tape which is near the each portion of the optical fiber individually. Accordingly, the any portion of the optical fiber does not need to pull the other portion and any portion does not need to endure a strong anti-tension. As the results, the optical transmission line of the present invention with small section area can easy to be inserted in the conduit for example the pipe of telephone line at the home by the house owner using his vacuum cleaner. As the optical fiber of the present invention, the plastic resin fiber covered by the light-reflection layer like a metal layer is prefer for decreasing the light beam like laser pulses which goes out of the strong bending portion of the optical fiber. By employing said optical transmission means of the present invention, the optical fiber can be arranged into the pipe with a small pulling force and the optical fiver does not have the damage from the pulling. This is the easy way to construct an optical Local Area Network in houses or buildings after they were built.